docs: def _get_pdf_list(self, input_pdfs):
          """
          Generate list of PDF documents.
  
          :param input_pdfs: List of PDFs or a directory path
               Directory - Scans directory contents
               List - Filters list to assert all list items are paths to PDF documents
          :return: List of PDF paths
          """
          if isinstance(input_pdfs, list):
              return [pdf for pdf in input_pdfs if self.validate(pdf)]
          elif os.path.isdir(input_pdfs):
              return [os.path.join(input_pdfs, pdf) for pdf in os.listdir(input_pdfs) if self.validate(pdf)]